1. Field of the Invention
The present invention relates to a resonant tag on which at least two resonant circuits having different resonant frequencies are formed and which can be identified by the detection of the resonant frequencies of the resonant circuits. The present invention also pertains to a method of manufacturing such a resonant tag.
2. Description of the Related Art
Conventionally, transportation of goods is conducted by utilizing railways, trucks, ships, airplanes and so on. In recent years, however, transportation of light-weight parcels by small trucks or the like, called Takuhaibin, have become very popular because of its low cost. In this type of transportation, a forwarding agent collects and delivers parcels to destinations in a short period of time. This transportation is known by its simple procedure and fast delivery of parcels.
In such transportation, parcels are attached with a label on which a sender, a destination and so on are filled in. A delivery man looks at the labels on the parcels and thereby checks the destinations and conducts sorting out of the parcels. Recently, checking of destinations and sorting out of the parcels have also been conducted in the following manners: in one method, destinations are coded, and sorting out of the parcels are conducted using the coded destinations. In another method, a delivery man carries with him or her a bar code system, and parcels carry on them a label on which bar codes representing a sender, destination and so on are printed.
However, in this transportation method, parcels are often delivered to a wrong destination or lost before they reach the destinations. Such accidents cost a forwarding agent substantial sums of money for investigation and compensation.
These accidents may be decreased by reinforcing visual checking of parcels. However, reinforcement of visual checking of parcels increases cost and prolongs the time for delivery. In any way, it requires manpower and limits reliability.
Furthermore, in a case where parcels are attached with a label on which a bar code is printed, the label must be in a state in which it can be optically read.
In other words, in order to read the bar code, the parcel must be positioned such that the surface thereof on which the bar code is printed is turned upward. If the surface with the label is turned downward, the bar code cannot be read, causing delivery of the parcel to an incorrect destination.
Furthermore, there is a limitation to the degree at which a bar code is read: if a label is adhered to an irregular surface, the bar code may be read incorrectly. This limits the size of the parcel on which the label is pasted.